blue plains advanced wastewater treatment plant A resource recovery facility. Transforming wastewater into clean water and energy. dcwater.com Facts at a Glance: Blue Plains Advanced Wastewater Treatment Plant Advanced Wastewater Treatment DC Water’s Blue Plains Advanced Wastewater Treatment Plant is the largest plant of its kind in the world, averaging 370 million treated gallons per day, and over one billion gallons per day at peak flow. •Service area covers more than 725 square miles. •Serves the population of the District of Columbia on a retail basis. Serves the region on a wholesale basis, providing treatment for more than 1.6 million people in Montgomery and Prince George’s counties in Maryland and Loudoun and Fairfax counties in Virginia. More than 17 million annual visitors. 370 million gallons. Enough to fill RFK Stadium daily. •Capacity to treat an average of 370 million gallons per day (mgd). While larger plants employ primary and secondary treatment, and stop there, Blue Plains provides advanced treatment – nitrification and denitrification, multimedia filtration and chlorination/dechlorination. The plant opened as a primary treatment facility in 1937 and added processes, technology and capacity in subsequent years. The facility continues to expand with new environmental and sustainable energy projects, using all 153 acres. •Peak wet weather capacity to treat 1.076 billion gallons per day. •DC Water uses both contracted and on-site laboratories to analyze samples and meet federal, state and local regulatory requirements. The in-house lab conducts more than 100,000 tests a year. •Biosolids are generated and beneficially reused. Currently, the Class B biosolids are land applied, supporting agriculture, silviculture, mine reclamation and compost production. In 2014, the biosolids will be anaerobically digested, converting the organic matter to methane for generation of heat and power to help power the plant. The remaining half of the solids will be processed into Class A biosolids with even greater reuse potential. In 2012, Blue Plains celebrates 75 years. facilities managed by, and service areas served by, dc water inside : welcome 1 FACTS AT A GLANCE 2 EVOLUTION OF WASTEWATER TREATMENT 3 THE COST OF ENVIRONMENTAL STEWARDSHIP 4-7 THE WASTEWATER TREATMENT PROCESS 8-9 NEXT GENERATION PROJECTS 1 Evolution of Wastewater Treatment The Cost of Environmental Stewardship Differential cost per additional lb DIFFERENTIAL COST PER POUND OF TOTAL NITROGEN REMOVED $51.49 per lb $50.00 $40.00 $30.00 $20.00 $10.00 $0.84 per lb 0 14.0 mg/L to 7.5 mg/L $3.69 per lb 7.5 mg/L to 5.0 mg/L 5.0 mg/L to 3.9 mg/L Nitrogen concentration achieved Before 1937, wastewater flowed through the District in open sewers and discharged untreated to the nearest waterway. Before sewers, disposal methods were even more primitive, contributing to epidemics of cholera and dysentery that caused a high death rate. Sewage conveyance and treatment, and the sanitation they brought to the District, were heralded for public health, quality of life and economic benefits. Blue Plains’ treatment provided the first barrier to protect the environment from wastewater generated by those living or working in the region. Half a century later, local waterways were suffering from the population growth of the District and upstream suburbs. Urban and suburban runoff, agricultural runoff and wastewater degraded the health of the Potomac and Anacostia rivers, Rock Creek and the Chesapeake Bay. The Blue Plains Advanced Wastewater Treatment Plant remains the best protection for our waterways, as it cleanses the wastewater generated by more than 2 million people, every minute of every day. The plant serves as a barrier to the receiving waters, minimizing the environmental impact of the things we do in our daily lives—not only using the toilet, but washing our clothes, our cars, our dishes, our food, our bodies and our teeth. It is a great service for the region. Environmental protection is an ongoing commitment. The engineers at DC Water continually examine wastewater technology and facilities to remain on the cutting edge and to implement innovative solutions. DC Water has three massive environmental wastewater programs underway, totaling $4 billion. We are committed to improving the health of local waterways, and generating sustainable energy from the wastewater treatment process. 2011 NITROGEN LOADS TO THE BAY BY JURISDICTION mil lbs/yr DC Water joined the Chesapeake Bay Agreement and was the first in the watershed to meet its voluntary program goals for nutrient removal of 40 percent of the 1985 levels, or 7.5 mg/L, two years ahead of schedule. With the current construction of enhanced nutrient removal facilities, the plant is on track to meet its nitrogen goals under the Chesapeake Bay Agreement 2000. The plant already meets its phosphorus goals, as phosphorus is captured in primary and secondary treatment and stored in biosolids which are land applied, recycling this valuable nutrient back to the land. DC Water continues to meet or exceed performance levels set by the U.S. EPA. Customers bear the bulk of the costs of these environmental protections. DC Water has received federal funding in the tens of millions of dollars for the three current environmental projects under construction at Blue Plains, but their ultimate price tag is about $4 billion. 46% PA 25% VA 20% MD 4% NY 2% WV It is important to note that even if nitrogen levels at Blue Plains were reduced to zero, local waterways and the Chesapeake Bay would still be impaired by other sources of nitrogen. Blue Plains contributes less than two percent of the estimated nitrogen load to the Chesapeake Bay. Although Blue Plains is the largest single point-source discharger of nitrogen, the vast majority of the nitrogen in the Bay is from non-point sources. 2% DE 1% DC 2011 NITROGEN LOADS TO THE BAY BY SOURCE mil lbs/yr It is imperative that other sources of nitrogen, including agricultural runoff, and urban and suburban runoff, are addressed to improve the health of local waters. States in the Chesapeake Bay watershed are formulating watershed implementation plans to do just that, but many are finding the solutions to be cost-prohibitive. 40% agriculture 25% atmospheric deposition 17% wastewater treatment plants Blue Plains less than 2% 15% urban / suburban runoff 3% septic 2 The cost of innovation and stewardship is significant. For example, the Blue Plains discharge permit issued by the United States Environmental Protection Agency (U.S. EPA) has three times required the Authority to dramatically reduce the level of nitrogen. This has been achieved through technological and engineering projects. As the nitrogen limits are further reduced, the price increases exponentially. The enhanced nitrogen removal project that is now underway will cost close to $1 billion and is at the limit of technology. State-of-the-Art Technology and Innovative Research As part of the nearly $1 billion plant-wide upgrades in the 2000s, the Authority streamlined operations by automating many processes and built a state-of-the-art operations center, where performance of the entire plant can be monitored. Blue Plains is world-renowned for its research programs that analyze technologies years before they are put into practice. DC Water’s engineering team is recognized for innovation, exploring technologies that have not been adopted in the United States. In fact, delegations of international wastewater engineers visit Blue Plains all year long to learn more about DC Water’s management, engineering, finance, research and technology. 3 The Wastewater Treatment Process Screening and grit removal Wastewater comes to Blue Plains through 1,800 miles of sewers from around the District and from the Potomac Interceptor, a large sewer that begins at Dulles Airport, bringing with it wastewater from suburbs along the way. At the headworks, the sewage is pumped up from below ground for treatment at the plant. A series of screens removes objects and large particles. The grit chamber removes rocks and other non-degradable particles. These are loaded into trucks and taken to a landfill. The wastewater then flows to the next stage of treatment. Primary clarifiers Primary treatment is a physical process that takes place in a coneshaped tank. Solid particles settle out and fall to the bottom, while the wastewater flows outward, over a set of weirs. An arm skims the fats, oils and grease (FOG) off the top while the solids settle to the bottom. This FOG is sent to landfills, while the solids are treated for reuse. Secondary reactors and sedimentation Secondary treatment is a biological process that uses microbes to treat organic material (fats, sugars, shortchain carbon molecules). At Blue Plains, activated sludge is the process used to achieve secondary treatment. For the process to be most effective, the microbes need both oxygen and food. Blue Plains supplies the oxygen by pumping air into the tanks with bubble diffusers. The wastewater contains the food (organic matter, or carbon). The microbes consume this food and grow more microbes. The added oxygen causes the 4 wastewater in secondary reactors to have a bubbling, active appearance and the microbes cause a reddishbrown color. aerated (anoxic). The microbes require a carbon source as food. Methanol is added in this process as the carbon source. It is a delicate environment that requires diligent monitoring to ensure the health of the microbial colonies. Once they have done their duty, the bugs are settled out from the wastewater in secondary sedimentation tanks. A portion of the settled microbes are then reintroduced to secondary reactors to sustain the process, with the remainder recycled with the biosolids. Multimedia filtration and disinfection Many wastewater treatment plants stop treatment here. But Blue Plains discharges to the Potomac, a tributary to the Chesapeake Bay, and nitrogen must be further removed to protect the watersheds. Nitrification, denitrification, filtration and disinfection establish Blue Plains as an advanced wastewater treatment facility. Nitrification The first step of tertiary treatment is oxidizing the nitrogen from ammonia to nitrate. This is achieved through another biological process using microbes in the nitrification reactors with a large amount of air. Denitrification The second step to nitrogen removal requires converting the nitrate to nitrogen gas, which releases the nitrogen safely into the atmosphere. This step does not add oxygen, which causes the microbes to consume the oxygen in nitrates. The process is achieved in the same type of tanks as nitrification, but the nitrification section is aerated (aerobic), while the denitrification section is not The treated plant flow is filtered through sand and anthracite in the world’s largest wastewater filtration facility. The flow is disinfected with sodium hypochlorite-based chlorination at the filter influent, and the residual chlorine is removed before discharge with sodium bisulfite. The final plant effluent after processing looks the same as drinking water. Sludge Thickening, Dewatering In the treatment processes, sludge is removed from process tanks. In the primary clarifiers, this sludge is sent to screening and grit removal, and then sent to gravity thickeners for thickening. Secondary or final effluent is used for dilution water for the gravity thickening process. before loading onto trucks and hauled to farmlands. The biosolids are land-applied, recycling the carbon and nutrients—nitrogen and phosphorus—back to the soil. The biosolids meet Class B quality standards, allowing for land application with strict requirements including buffer zones and a access limitation. The future for biosolids at DC Water is even brighter with the construction of new facilities to process them and generate combined heat and power. The biosolids will be batch treated at high temperatures and pressure and then fed to anaerobic digesters. The digester will capture methane and burn it in a turbine, providing net 10 MW of electricity and steam to heat the process. Sludge that comes from the secondary and nitrification processes is sent to dissolved air flotation tanks where a process using supersaturated air is able to float the sludge to the surface. This secondary sludge is skimmed off the surface and combined with the gravity thickened sludge in a blend tank and then fed to centrifuges to remove as much liquid as possible, leaving a biosolid cake. This process is called dewatering and is achieved by sending the sludges through high-speed centrifuges that separate out the water and solids. Biosolids End Use For many years, the final process for biosolids has involved treating them with lime to stabilize the solids and reduce residual pathogens 5 The Wastewater Treatment Process source influent screens influent pumping aerated grit chamber primary sedimentation tanks air secondary reactors secondary sedimentation tanks air nitrification denitrification reactors air nitrification / denitrification sedimentation tanks mixing landfill filter influent pumps nutrients and carbon recycling silviculture gravity sludge thickening GROWTH BEFORE BIOSOLIDS GROWTH AFTER BIOSOLIDS 20 YEARS 9 YEARS Increases yield and improves understory. dissolved air flotation thickening multimedia filters Under Construction Enhanced Nutrient Removal– see page 8 for details BIOSOLIDS APPLIED AT THIS TIME centrifuge dewatering disinfectant tanks farming Under construction: Clean Rivers Project– see page 9 for details Provides carbon and nutrients valued at $300.00 per acre. dechlorination reclamation Restoring mines to their natural state and providing wildlife habitats. Under construction: Thermal Hydrolysis and Anaerobic Digestion lime stabilization (mixer) – see page 8 for details urban restoration land applications Use compost to grow trees and reduce runoff. 6 7 Next Generation Projects Enhanced Nutrient Removal The enhanced nutrient removal project’s mission is to reduce the level of nitrogen from the cleansed wastewater that DC Water discharges to the Potomac River. Nitrogen can act as a fertilizer in the Potomac River and Chesapeake Bay, creating unruly grasses that deplete oxygen needed by marine life to live and thrive. Once the $950 million project is complete, Blue Plains will produce effluent with some of the lowest levels of nitrogen in the country. At 4 milligrams per liter (mg/L), it is extremely low, and is considered near the limit of conventional treatment technology. The facilities include more than 40 million gallons of additional anoxic reactor capacity for nitrogen removal, new post-aeration facilities, an 890 mgd lift station, new channels and conveyance structures, and new facilities to store and feed methanol and alternative carbon sources. Thermal Hydrolysis and Anaerobic Digestion DC Water will be the first utility in North America to use thermal hydrolysis for wastewater treatment. When completed, it will be the largest thermal hydrolysis plant in the world. Though thermal hydrolysis has been employed in Europe, the water sector in North America has not yet adopted this technology. Industry leaders across the continent eagerly await the results for the potential of using this technology. The process pressure-cooks the solids left over after wastewater treatment to produce combined heat and power—generating a net 10 MW of electricity. DC Water is the largest single source consumer of electricity in the District, and the digesters should cut consumption up to a third. The process will also create a Class A biosolid that has many more reuse options as a soil amendment than the current Class B product. The solids product is a smaller volume, and even when land-applied, will reduce hauling and emissions, further reducing the plant’s carbon footprint by a third. How much energy is 10 MW? That’s enough to power 8,000 homes. As in many older cities, about onethird of the District has a combined sewer system, meaning one pipe carries both wastewater and storm runoff. A combined-sewer overflow (or CSO) occurs during heavy rain when the mixture of sewage and stormwater cannot fit in the sewer pipes and overflows to the nearest water body. CSOs direct about 2.5 billion gallons of combined sewage into the Anacostia and Potomac rivers and Rock Creek in an average year. CSOs contain bacteria and trash that can be harmful to the environment. DC Water has already reduced CSOs to the Anacostia River by 40 percent with improvements to the existing sewer system. To achieve a 98 percent capture rate, the Clean Rivers Project will consist of massive underground tunnels to store the combined sewage during rain events, releasing it to Blue Plains after the storms subside. The first and largest tunnel system will serve the Anacostia River. This tunnel will be 23 feet in diameter and will run more than 100 feet deep, along the Potomac and under the Anacostia. The tunnel segments south of RFK Stadium, together with their surface hydraulic facilities and a tunnel dewatering pump station, are scheduled to begin operating in 2018, providing relief to the Anacostia River first. DC Water is proposing a pilot Green Infrastructure (GI) program to test the ability of GI—trees, tree boxes, rain barrels, porous pavers, rain gardens, etc.— to control enough runoff that the final two tunnels may be minimized. A GI solution would benefit the District with a lower cost solution along with green jobs, a greener DC, and cleaner waterways. 8 dcwater.com